Look, LE really got the public involved in this case. I agree that LE's only "real" responsibility is to investigate this case, but when any person or organization asks for (and gets) the assistance of the public at large, then they should expect that there will be a huge response from the public at large when the case turns out like this. LE and the investigators of this case have an ethical duty at this point to address the public and at the very least try and put an end to some of the nastiness that is infecting the online discussions at this point. Heck, they could even lie in order to do that. "At this point, we have no reason to believe that Abby was pregnant" or "As of now, we have asked the family and Abby not to give interviews or address the public" or "We understand that we have asked for assistance using vague and cryptic information. We regret that is all we can give you right now, but your help stills means a lot to us and to the family".
To me, any of those things would really go a long way right now.